Controlled tissue ablation

Abstract

A catheter ( 28 ) has a distal portion that comprises an electrode unit ( 22 ) and an ablation unit ( 24 ). A control unit ( 32 ) is configured: (i) to receive a preliminary blood pressure value (BPV), (ii) to receive a target excited BPV, (iii) to iteratively: (a) drive the electrode unit to apply an excitatory current to nerve of a renal artery ( 8 ), (b) receive a detected excited BPV, and (c) alter a value of a property of the excitatory current, until the detected excited BPV crosses a first threshold, and (iv) subsequently, to iteratively: (d) drive the ablation unit to apply ablating energy to the nerve, (e) subsequently, drive the electrode unit to apply a selected excitatory current to the nerve, and (f) receive a detected ablated BPV, until the detected ablated BPV crosses a second threshold. Other embodiments are also described.

The invention claimed is: 
     
       1. Apparatus for facilitating ablation of nerve tissue of a subject, the apparatus comprising:
 an ablation unit, configured to be percutaneously advanced to a site adjacent to a first portion of the nerve tissue of the subject; 
 at least one electrode unit, coupled to the ablation unit, and configured to be percutaneously advanced to a site adjacent to a second portion of the nerve tissue of the subject, and to initiate unidirectional action potentials in the nerve tissue, such that the unidirectional action potentials propagate toward the first portion of the nerve tissue; and 
 a control unit, configured:
 to drive the ablation unit to ablate, at least in part, the first portion of the nerve tissue of the subject, and 
 to drive the at least one electrode unit to initiate the unidirectional action potentials by applying an excitatory current to the second portion of the nerve tissue. 
 
 
     
     
       2. The apparatus according to  claim 1 , wherein the at least one electrode unit comprises a first electrode unit and a second electrode unit, the first electrode unit being coupled to the ablation unit on a first side of the ablation unit, and the second electrode unit being coupled to the ablation unit on a second side of the ablation unit, each electrode unit being configured to initiate unidirectional action potentials in the nerve tissue, such that the action potentials propagate toward the first portion of the nerve tissue. 
     
     
       3. The apparatus according to  claim 1 , wherein the ablation unit comprises a radio-frequency ablation unit, and wherein the control unit is configured to drive the radio-frequency ablation unit to ablate the first portion of the nerve tissue by applying an ablative radio-frequency current to the first portion of the nerve tissue. 
     
     
       4. The apparatus according to  claim 1 , wherein the ablation unit comprises an ultrasound ablation unit, and wherein the control unit is configured to drive the ultrasound ablation unit to ablate the first portion of the nerve tissue by applying ablative ultrasound energy to the first portion of the nerve tissue. 
     
     
       5. The apparatus according to  claim 1 , wherein the electrode unit is configured to apply a non-ablative blocking current to the second portion of the nerve tissue of the subject, the non-ablative blocking current being configured to reversibly block endogenous action potentials from propagating through the second portion of the nerve tissue, and wherein the control unit is configured to drive the at least one electrode unit to apply the non-ablative blocking current. 
     
     
       6. The apparatus according to  claim 1 , wherein the site includes a blood vessel, the nerve tissue includes nerve tissue of the blood vessel, and the at least one electrode unit comprises a plurality of sub-electrodes configured to be arranged in a broken arc that traces an inner wall of the blood vessel. 
     
     
       7. The apparatus according to  claim 6 , wherein the control unit is configured to drive the plurality of sub-electrodes to simultaneously apply the excitatory current. 
     
     
       8. The apparatus according to  claim 7 , wherein each of the plurality of sub-electrodes is independently addressable by the control unit. 
     
     
       9. The apparatus according to  claim 7 , wherein the control unit is configured to balance the excitatory current across the plurality of sub-electrodes. 
     
     
       10. The apparatus according to  claim 1 , wherein the nerve tissue includes nerve tissue of a blood vessel of the subject, and wherein at least the ablation unit is configured to be transluminally delivered to the blood vessel of the subject. 
     
     
       11. The apparatus according to  claim 10 , wherein the electrode unit is configured to be transluminally delivered to the blood vessel of the subject. 
     
     
       12. The apparatus according to  claim 10 , wherein the blood vessel includes a renal artery of the subject, and wherein at least the ablation unit is configured to be transluminally delivered to the renal artery of the subject. 
     
     
       13. The apparatus according to  claim 1 , further comprising a longitudinal member, having a distal portion that is configured to be percutaneously advanced toward the nerve tissue of the subject, and wherein the ablation unit and the at least one electrode unit are coupled to the longitudinal member. 
     
     
       14. The apparatus according to  claim 13 , wherein:
 the ablation unit comprises a first ablation unit, and the at least one electrode unit comprises a respective first at least one electrode unit, 
 the apparatus further comprises a second ablation unit and a second respective at least one electrode unit, and 
 the distal portion of the longitudinal member is bifurcated so as to have (i) a first distal portion that is coupled to the first ablation unit and the first at least one electrode unit, and (ii) a second distal portion that is coupled to the second ablation unit and the second at least one electrode unit, each of the distal portions being configured to be transluminally advanced into a respective renal artery of the subject. 
 
     
     
       15. The apparatus according to  claim 1 , further comprising a sensor, configured to detect a physiological response of the subject to the unidirectional action potentials initiated by the electrode unit. 
     
     
       16. The apparatus according to  claim 15 , further comprising a longitudinal member, configured to be percutaneously advanced toward the nerve tissue of the subject, and wherein the ablation unit, the electrode unit, and the sensor are coupled to the longitudinal member. 
     
     
       17. The apparatus according to  claim 15 , wherein the sensor is configured to be disposed in an aorta of the subject. 
     
     
       18. The apparatus according to  claim 15 , wherein the sensor comprises a blood pressure sensor. 
     
     
       19. The apparatus according to  claim 15 , wherein the control unit is configured to receive information indicative of the detected physiological response, and to drive the ablation unit at least in part responsively to the information indicative of the detected physiological response. 
     
     
       20. The apparatus according to  claim 19 , wherein the control unit is configured:
 to drive, during a first period, the at least one electrode unit to apply a non-ablative blocking current to the second portion of the nerve tissue of the subject, the blocking current being configured to temporarily block endogenous action potentials from propagating through the second portion of the nerve tissue, 
 to receive a first value of a factor indicative of the response, the first value being detected after a start of the application of the non-ablative blocking current, and 
 to drive the ablation unit at least in part responsively to the received first value. 
 
     
     
       21. The apparatus according to  claim 20 , wherein the control unit is configured:
 to drive, during a second period, the at least one electrode unit to apply the excitatory current, 
 to receive a second value of the factor, the second value being detected after a start of the application of the excitatory current, and 
 to drive the ablation unit at least in part responsively to the received second value. 
 
     
     
       22. The apparatus according to  claim 20 , wherein the sensor is configured to detect the first value of the factor after the start of the application of the non-ablative blocking current, and to provide the first value of the factor to the control unit.